includes/libs/filebackend/FileBackend.php

   1 <?php
   2 /**
   3  * @defgroup FileBackend File backend
   4  *
   5  * File backend is used to interact with file storage systems,
   6  * such as the local file system, NFS, or cloud storage systems.
   7  */
   8
   9 /**
  10  * Base class for all file backends.
  11  *
  12  * This program is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU General Public License as published by
  14  * the Free Software Foundation; either version 2 of the License, or
  15  * (at your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  20  * GNU General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License along
  23  * with this program; if not, write to the Free Software Foundation, Inc.,
  24  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  25  * http://www.gnu.org/copyleft/gpl.html
  26  *
  27  * @file
  28  * @ingroup FileBackend
  29  * @author Aaron Schulz
  30  */
  31 use Psr\Log\LoggerAwareInterface;
  32 use Psr\Log\LoggerInterface;
  33
  34 /**
  35  * @brief Base class for all file backend classes (including multi-write backends).
  36  *
  37  * This class defines the methods as abstract that subclasses must implement.
  38  * Outside callers can assume that all backends will have these functions.
  39  *
  40  * All "storage paths" are of the format "mwstore://<backend>/<container>/<path>".
  41  * The "backend" portion is unique name for the application to refer to a backend, while
  42  * the "container" portion is a top-level directory of the backend. The "path" portion
  43  * is a relative path that uses UNIX file system (FS) notation, though any particular
  44  * backend may not actually be using a local filesystem. Therefore, the relative paths
  45  * are only virtual.
  46  *
  47  * Backend contents are stored under "domain"-specific container names by default.
  48  * A domain is simply a logical umbrella for entities, such as those belonging to a certain
  49  * application or portion of a website, for example. A domain can be local or global.
  50  * Global (qualified) backends are achieved by configuring the "domain ID" to a constant.
  51  * Global domains are simpler, but local domains can be used by choosing a domain ID based on
  52  * the current context, such as which language of a website is being used.
  53  *
  54  * For legacy reasons, the FSFileBackend class allows manually setting the paths of
  55  * containers to ones that do not respect the "domain ID".
  56  *
  57  * In key/value (object) stores, containers are the only hierarchy (the rest is emulated).
  58  * FS-based backends are somewhat more restrictive due to the existence of real
  59  * directory files; a regular file cannot have the same name as a directory. Other
  60  * backends with virtual directories may not have this limitation. Callers should
  61  * store files in such a way that no files and directories are under the same path.
  62  *
  63  * In general, this class allows for callers to access storage through the same
  64  * interface, without regard to the underlying storage system. However, calling code
  65  * must follow certain patterns and be aware of certain things to ensure compatibility:
  66  *   - a) Always call prepare() on the parent directory before trying to put a file there;
  67  *        key/value stores only need the container to exist first, but filesystems need
  68  *        all the parent directories to exist first (prepare() is aware of all this)
  69  *   - b) Always call clean() on a directory when it might become empty to avoid empty
  70  *        directory buildup on filesystems; key/value stores never have empty directories,
  71  *        so doing this helps preserve consistency in both cases
  72  *   - c) Likewise, do not rely on the existence of empty directories for anything;
  73  *        calling directoryExists() on a path that prepare() was previously called on
  74  *        will return false for key/value stores if there are no files under that path
  75  *   - d) Never alter the resulting FSFile returned from getLocalReference(), as it could
  76  *        either be a copy of the source file in /tmp or the original source file itself
  77  *   - e) Use a file layout that results in never attempting to store files over directories
  78  *        or directories over files; key/value stores allow this but filesystems do not
  79  *   - f) Use ASCII file names (e.g. base32, IDs, hashes) to avoid Unicode issues in Windows
  80  *   - g) Do not assume that move operations are atomic (difficult with key/value stores)
  81  *   - h) Do not assume that file stat or read operations always have immediate consistency;
  82  *        various methods have a "latest" flag that should always be used if up-to-date
  83  *        information is required (this trades performance for correctness as needed)
  84  *   - i) Do not assume that directory listings have immediate consistency
  85  *
  86  * Methods of subclasses should avoid throwing exceptions at all costs.
  87  * As a corollary, external dependencies should be kept to a minimum.
  88  *
  89  * @ingroup FileBackend
  90  * @since 1.19
  91  */
  92 abstract class FileBackend implements LoggerAwareInterface {
  93         /** @var string Unique backend name */
  94         protected $name;
  95
  96         /** @var string Unique domain name */
  97         protected $domainId;
  98
  99         /** @var string Read-only explanation message */
 100         protected $readOnly;
 101
 102         /** @var string When to do operations in parallel */
 103         protected $parallelize;
 104
 105         /** @var int How many operations can be done in parallel */
 106         protected $concurrency;
 107
 108         /** @var string Temporary file directory */
 109         protected $tmpDirectory;
 110
 111         /** @var LockManager */
 112         protected $lockManager;
 113         /** @var FileJournal */
 114         protected $fileJournal;
 115         /** @var LoggerInterface */
 116         protected $logger;
 117         /** @var object|string Class name or object With profileIn/profileOut methods */
 118         protected $profiler;
 119
 120         /** @var callable */
 121         protected $obResetFunc;
 122         /** @var callable */
 123         protected $streamMimeFunc;
 124         /** @var callable */
 125         protected $statusWrapper;
 126
 127         /** Bitfield flags for supported features */
 128         const ATTR_HEADERS = 1; // files can be tagged with standard HTTP headers
 129         const ATTR_METADATA = 2; // files can be stored with metadata key/values
 130         const ATTR_UNICODE_PATHS = 4; // files can have Unicode paths (not just ASCII)
 131
 132         /**
 133          * Create a new backend instance from configuration.
 134          * This should only be called from within FileBackendGroup.
 135          *
 136          * @param array $config Parameters include:
 137          *   - name : The unique name of this backend.
 138          *      This should consist of alphanumberic, '-', and '_' characters.
 139          *      This name should not be changed after use (e.g. with journaling).
 140          *      Note that the name is *not* used in actual container names.
 141          *   - domainId : Prefix to container names that is unique to this backend.
 142          *      It should only consist of alphanumberic, '-', and '_' characters.
 143          *      This ID is what avoids collisions if multiple logical backends
 144          *      use the same storage system, so this should be set carefully.
 145          *   - lockManager : LockManager object to use for any file locking.
 146          *      If not provided, then no file locking will be enforced.
 147          *   - fileJournal : FileJournal object to use for logging changes to files.
 148          *      If not provided, then change journaling will be disabled.
 149          *   - readOnly : Write operations are disallowed if this is a non-empty string.
 150          *      It should be an explanation for the backend being read-only.
 151          *   - parallelize : When to do file operations in parallel (when possible).
 152          *      Allowed values are "implicit", "explicit" and "off".
 153          *   - concurrency : How many file operations can be done in parallel.
 154          *   - tmpDirectory : Directory to use for temporary files. If this is not set or null,
 155          *      then the backend will try to discover a usable temporary directory.
 156          *   - obResetFunc : alternative callback to clear the output buffer
 157          *   - streamMimeFunc : alternative method to determine the content type from the path
 158          *   - logger : Optional PSR logger object.
 159          *   - profiler : Optional class name or object With profileIn/profileOut methods.
 160          * @throws InvalidArgumentException
 161          */
 162         public function __construct( array $config ) {
 163                 $this->name = $config['name'];
 164                 $this->domainId = isset( $config['domainId'] )
 165                         ? $config['domainId'] // e.g. "my_wiki-en_"
 166                         : $config['wikiId']; // b/c alias
 167                 if ( !preg_match( '!^[a-zA-Z0-9-_]{1,255}$!', $this->name ) ) {
 168                         throw new InvalidArgumentException( "Backend name '{$this->name}' is invalid." );
 169                 } elseif ( !is_string( $this->domainId ) ) {
 170                         throw new InvalidArgumentException(
 171                                 "Backend domain ID not provided for '{$this->name}'." );
 172                 }
 173                 $this->lockManager = isset( $config['lockManager'] )
 174                         ? $config['lockManager']
 175                         : new NullLockManager( [] );
 176                 $this->fileJournal = isset( $config['fileJournal'] )
 177                         ? $config['fileJournal']
 178                         : FileJournal::factory( [ 'class' => 'NullFileJournal' ], $this->name );
 179                 $this->readOnly = isset( $config['readOnly'] )
 180                         ? (string)$config['readOnly']
 181                         : '';
 182                 $this->parallelize = isset( $config['parallelize'] )
 183                         ? (string)$config['parallelize']
 184                         : 'off';
 185                 $this->concurrency = isset( $config['concurrency'] )
 186                         ? (int)$config['concurrency']
 187                         : 50;
 188                 $this->obResetFunc = isset( $params['obResetFunc'] ) ? $params['obResetFunc'] : null;
 189                 $this->streamMimeFunc = isset( $params['streamMimeFunc'] )
 190                         ? $params['streamMimeFunc']
 191                         : null;
 192                 $this->statusWrapper = isset( $config['statusWrapper'] ) ? $config['statusWrapper'] : null;
 193
 194                 $this->profiler = isset( $params['profiler'] ) ? $params['profiler'] : null;
 195                 $this->logger = isset( $config['logger'] ) ? $config['logger'] : new \Psr\Log\NullLogger();
 196                 $this->statusWrapper = isset( $config['statusWrapper'] ) ? $config['statusWrapper'] : null;
 197                 $this->tmpDirectory = isset( $config['tmpDirectory'] ) ? $config['tmpDirectory'] : null;
 198         }
 199
 200         public function setLogger( LoggerInterface $logger ) {
 201                 $this->logger = $logger;
 202         }
 203
 204         /**
 205          * Get the unique backend name.
 206          * We may have multiple different backends of the same type.
 207          * For example, we can have two Swift backends using different proxies.
 208          *
 209          * @return string
 210          */
 211         final public function getName() {
 212                 return $this->name;
 213         }
 214
 215         /**
 216          * Get the domain identifier used for this backend (possibly empty).
 217          *
 218          * @return string
 219          * @since 1.28
 220          */
 221         final public function getDomainId() {
 222                 return $this->domainId;
 223         }
 224
 225         /**
 226          * Alias to getDomainId()
 227          * @return string
 228          * @since 1.20
 229          */
 230         final public function getWikiId() {
 231                 return $this->getDomainId();
 232         }
 233
 234         /**
 235          * Check if this backend is read-only
 236          *
 237          * @return bool
 238          */
 239         final public function isReadOnly() {
 240                 return ( $this->readOnly != '' );
 241         }
 242
 243         /**
 244          * Get an explanatory message if this backend is read-only
 245          *
 246          * @return string|bool Returns false if the backend is not read-only
 247          */
 248         final public function getReadOnlyReason() {
 249                 return ( $this->readOnly != '' ) ? $this->readOnly : false;
 250         }
 251
 252         /**
 253          * Get the a bitfield of extra features supported by the backend medium
 254          *
 255          * @return int Bitfield of FileBackend::ATTR_* flags
 256          * @since 1.23
 257          */
 258         public function getFeatures() {
 259                 return self::ATTR_UNICODE_PATHS;
 260         }
 261
 262         /**
 263          * Check if the backend medium supports a field of extra features
 264          *
 265          * @param int $bitfield Bitfield of FileBackend::ATTR_* flags
 266          * @return bool
 267          * @since 1.23
 268          */
 269         final public function hasFeatures( $bitfield ) {
 270                 return ( $this->getFeatures() & $bitfield ) === $bitfield;
 271         }
 272
 273         /**
 274          * This is the main entry point into the backend for write operations.
 275          * Callers supply an ordered list of operations to perform as a transaction.
 276          * Files will be locked, the stat cache cleared, and then the operations attempted.
 277          * If any serious errors occur, all attempted operations will be rolled back.
 278          *
 279          * $ops is an array of arrays. The outer array holds a list of operations.
 280          * Each inner array is a set of key value pairs that specify an operation.
 281          *
 282          * Supported operations and their parameters. The supported actions are:
 283          *  - create
 284          *  - store
 285          *  - copy
 286          *  - move
 287          *  - delete
 288          *  - describe (since 1.21)
 289          *  - null
 290          *
 291          * FSFile/TempFSFile object support was added in 1.27.
 292          *
 293          * a) Create a new file in storage with the contents of a string
 294          * @code
 295          *     [
 296          *         'op'                  => 'create',
 297          *         'dst'                 => <storage path>,
 298          *         'content'             => <string of new file contents>,
 299          *         'overwrite'           => <boolean>,
 300          *         'overwriteSame'       => <boolean>,
 301          *         'headers'             => <HTTP header name/value map> # since 1.21
 302          *     ]
 303          * @endcode
 304          *
 305          * b) Copy a file system file into storage
 306          * @code
 307          *     [
 308          *         'op'                  => 'store',
 309          *         'src'                 => <file system path, FSFile, or TempFSFile>,
 310          *         'dst'                 => <storage path>,
 311          *         'overwrite'           => <boolean>,
 312          *         'overwriteSame'       => <boolean>,
 313          *         'headers'             => <HTTP header name/value map> # since 1.21
 314          *     ]
 315          * @endcode
 316          *
 317          * c) Copy a file within storage
 318          * @code
 319          *     [
 320          *         'op'                  => 'copy',
 321          *         'src'                 => <storage path>,
 322          *         'dst'                 => <storage path>,
 323          *         'overwrite'           => <boolean>,
 324          *         'overwriteSame'       => <boolean>,
 325          *         'ignoreMissingSource' => <boolean>, # since 1.21
 326          *         'headers'             => <HTTP header name/value map> # since 1.21
 327          *     ]
 328          * @endcode
 329          *
 330          * d) Move a file within storage
 331          * @code
 332          *     [
 333          *         'op'                  => 'move',
 334          *         'src'                 => <storage path>,
 335          *         'dst'                 => <storage path>,
 336          *         'overwrite'           => <boolean>,
 337          *         'overwriteSame'       => <boolean>,
 338          *         'ignoreMissingSource' => <boolean>, # since 1.21
 339          *         'headers'             => <HTTP header name/value map> # since 1.21
 340          *     ]
 341          * @endcode
 342          *
 343          * e) Delete a file within storage
 344          * @code
 345          *     [
 346          *         'op'                  => 'delete',
 347          *         'src'                 => <storage path>,
 348          *         'ignoreMissingSource' => <boolean>
 349          *     ]
 350          * @endcode
 351          *
 352          * f) Update metadata for a file within storage
 353          * @code
 354          *     [
 355          *         'op'                  => 'describe',
 356          *         'src'                 => <storage path>,
 357          *         'headers'             => <HTTP header name/value map>
 358          *     ]
 359          * @endcode
 360          *
 361          * g) Do nothing (no-op)
 362          * @code
 363          *     [
 364          *         'op'                  => 'null',
 365          *     ]
 366          * @endcode
 367          *
 368          * Boolean flags for operations (operation-specific):
 369          *   - ignoreMissingSource : The operation will simply succeed and do
 370          *                           nothing if the source file does not exist.
 371          *   - overwrite           : Any destination file will be overwritten.
 372          *   - overwriteSame       : If a file already exists at the destination with the
 373          *                           same contents, then do nothing to the destination file
 374          *                           instead of giving an error. This does not compare headers.
 375          *                           This option is ignored if 'overwrite' is already provided.
 376          *   - headers             : If supplied, the result of merging these headers with any
 377          *                           existing source file headers (replacing conflicting ones)
 378          *                           will be set as the destination file headers. Headers are
 379          *                           deleted if their value is set to the empty string. When a
 380          *                           file has headers they are included in responses to GET and
 381          *                           HEAD requests to the backing store for that file.
 382          *                           Header values should be no larger than 255 bytes, except for
 383          *                           Content-Disposition. The system might ignore or truncate any
 384          *                           headers that are too long to store (exact limits will vary).
 385          *                           Backends that don't support metadata ignore this. (since 1.21)
 386          *
 387          * $opts is an associative of boolean flags, including:
 388          *   - force               : Operation precondition errors no longer trigger an abort.
 389          *                           Any remaining operations are still attempted. Unexpected
 390          *                           failures may still cause remaining operations to be aborted.
 391          *   - nonLocking          : No locks are acquired for the operations.
 392          *                           This can increase performance for non-critical writes.
 393          *                           This has no effect unless the 'force' flag is set.
 394          *   - nonJournaled        : Don't log this operation batch in the file journal.
 395          *                           This limits the ability of recovery scripts.
 396          *   - parallelize         : Try to do operations in parallel when possible.
 397          *   - bypassReadOnly      : Allow writes in read-only mode. (since 1.20)
 398          *   - preserveCache       : Don't clear the process cache before checking files.
 399          *                           This should only be used if all entries in the process
 400          *                           cache were added after the files were already locked. (since 1.20)
 401          *
 402          * @remarks Remarks on locking:
 403          * File system paths given to operations should refer to files that are
 404          * already locked or otherwise safe from modification from other processes.
 405          * Normally these files will be new temp files, which should be adequate.
 406          *
 407          * @par Return value:
 408          *
 409          * This returns a Status, which contains all warnings and fatals that occurred
 410          * during the operation. The 'failCount', 'successCount', and 'success' members
 411          * will reflect each operation attempted.
 412          *
 413          * The StatusValue will be "OK" unless:
 414          *   - a) unexpected operation errors occurred (network partitions, disk full...)
 415          *   - b) significant operation errors occurred and 'force' was not set
 416          *
 417          * @param array $ops List of operations to execute in order
 418          * @param array $opts Batch operation options
 419          * @return StatusValue
 420          */
 421         final public function doOperations( array $ops, array $opts = [] ) {
 422                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 423                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 424                 }
 425                 if ( !count( $ops ) ) {
 426                         return $this->newStatus(); // nothing to do
 427                 }
 428
 429                 $ops = $this->resolveFSFileObjects( $ops );
 430                 if ( empty( $opts['force'] ) ) { // sanity
 431                         unset( $opts['nonLocking'] );
 432                 }
 433
 434                 /** @noinspection PhpUnusedLocalVariableInspection */
 435                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 436
 437                 return $this->doOperationsInternal( $ops, $opts );
 438         }
 439
 440         /**
 441          * @see FileBackend::doOperations()
 442          * @param array $ops
 443          * @param array $opts
 444          */
 445         abstract protected function doOperationsInternal( array $ops, array $opts );
 446
 447         /**
 448          * Same as doOperations() except it takes a single operation.
 449          * If you are doing a batch of operations that should either
 450          * all succeed or all fail, then use that function instead.
 451          *
 452          * @see FileBackend::doOperations()
 453          *
 454          * @param array $op Operation
 455          * @param array $opts Operation options
 456          * @return StatusValue
 457          */
 458         final public function doOperation( array $op, array $opts = [] ) {
 459                 return $this->doOperations( [ $op ], $opts );
 460         }
 461
 462         /**
 463          * Performs a single create operation.
 464          * This sets $params['op'] to 'create' and passes it to doOperation().
 465          *
 466          * @see FileBackend::doOperation()
 467          *
 468          * @param array $params Operation parameters
 469          * @param array $opts Operation options
 470          * @return StatusValue
 471          */
 472         final public function create( array $params, array $opts = [] ) {
 473                 return $this->doOperation( [ 'op' => 'create' ] + $params, $opts );
 474         }
 475
 476         /**
 477          * Performs a single store operation.
 478          * This sets $params['op'] to 'store' and passes it to doOperation().
 479          *
 480          * @see FileBackend::doOperation()
 481          *
 482          * @param array $params Operation parameters
 483          * @param array $opts Operation options
 484          * @return StatusValue
 485          */
 486         final public function store( array $params, array $opts = [] ) {
 487                 return $this->doOperation( [ 'op' => 'store' ] + $params, $opts );
 488         }
 489
 490         /**
 491          * Performs a single copy operation.
 492          * This sets $params['op'] to 'copy' and passes it to doOperation().
 493          *
 494          * @see FileBackend::doOperation()
 495          *
 496          * @param array $params Operation parameters
 497          * @param array $opts Operation options
 498          * @return StatusValue
 499          */
 500         final public function copy( array $params, array $opts = [] ) {
 501                 return $this->doOperation( [ 'op' => 'copy' ] + $params, $opts );
 502         }
 503
 504         /**
 505          * Performs a single move operation.
 506          * This sets $params['op'] to 'move' and passes it to doOperation().
 507          *
 508          * @see FileBackend::doOperation()
 509          *
 510          * @param array $params Operation parameters
 511          * @param array $opts Operation options
 512          * @return StatusValue
 513          */
 514         final public function move( array $params, array $opts = [] ) {
 515                 return $this->doOperation( [ 'op' => 'move' ] + $params, $opts );
 516         }
 517
 518         /**
 519          * Performs a single delete operation.
 520          * This sets $params['op'] to 'delete' and passes it to doOperation().
 521          *
 522          * @see FileBackend::doOperation()
 523          *
 524          * @param array $params Operation parameters
 525          * @param array $opts Operation options
 526          * @return StatusValue
 527          */
 528         final public function delete( array $params, array $opts = [] ) {
 529                 return $this->doOperation( [ 'op' => 'delete' ] + $params, $opts );
 530         }
 531
 532         /**
 533          * Performs a single describe operation.
 534          * This sets $params['op'] to 'describe' and passes it to doOperation().
 535          *
 536          * @see FileBackend::doOperation()
 537          *
 538          * @param array $params Operation parameters
 539          * @param array $opts Operation options
 540          * @return StatusValue
 541          * @since 1.21
 542          */
 543         final public function describe( array $params, array $opts = [] ) {
 544                 return $this->doOperation( [ 'op' => 'describe' ] + $params, $opts );
 545         }
 546
 547         /**
 548          * Perform a set of independent file operations on some files.
 549          *
 550          * This does no locking, nor journaling, and possibly no stat calls.
 551          * Any destination files that already exist will be overwritten.
 552          * This should *only* be used on non-original files, like cache files.
 553          *
 554          * Supported operations and their parameters:
 555          *  - create
 556          *  - store
 557          *  - copy
 558          *  - move
 559          *  - delete
 560          *  - describe (since 1.21)
 561          *  - null
 562          *
 563          * FSFile/TempFSFile object support was added in 1.27.
 564          *
 565          * a) Create a new file in storage with the contents of a string
 566          * @code
 567          *     [
 568          *         'op'                  => 'create',
 569          *         'dst'                 => <storage path>,
 570          *         'content'             => <string of new file contents>,
 571          *         'headers'             => <HTTP header name/value map> # since 1.21
 572          *     ]
 573          * @endcode
 574          *
 575          * b) Copy a file system file into storage
 576          * @code
 577          *     [
 578          *         'op'                  => 'store',
 579          *         'src'                 => <file system path, FSFile, or TempFSFile>,
 580          *         'dst'                 => <storage path>,
 581          *         'headers'             => <HTTP header name/value map> # since 1.21
 582          *     ]
 583          * @endcode
 584          *
 585          * c) Copy a file within storage
 586          * @code
 587          *     [
 588          *         'op'                  => 'copy',
 589          *         'src'                 => <storage path>,
 590          *         'dst'                 => <storage path>,
 591          *         'ignoreMissingSource' => <boolean>, # since 1.21
 592          *         'headers'             => <HTTP header name/value map> # since 1.21
 593          *     ]
 594          * @endcode
 595          *
 596          * d) Move a file within storage
 597          * @code
 598          *     [
 599          *         'op'                  => 'move',
 600          *         'src'                 => <storage path>,
 601          *         'dst'                 => <storage path>,
 602          *         'ignoreMissingSource' => <boolean>, # since 1.21
 603          *         'headers'             => <HTTP header name/value map> # since 1.21
 604          *     ]
 605          * @endcode
 606          *
 607          * e) Delete a file within storage
 608          * @code
 609          *     [
 610          *         'op'                  => 'delete',
 611          *         'src'                 => <storage path>,
 612          *         'ignoreMissingSource' => <boolean>
 613          *     ]
 614          * @endcode
 615          *
 616          * f) Update metadata for a file within storage
 617          * @code
 618          *     [
 619          *         'op'                  => 'describe',
 620          *         'src'                 => <storage path>,
 621          *         'headers'             => <HTTP header name/value map>
 622          *     ]
 623          * @endcode
 624          *
 625          * g) Do nothing (no-op)
 626          * @code
 627          *     [
 628          *         'op'                  => 'null',
 629          *     ]
 630          * @endcode
 631          *
 632          * @par Boolean flags for operations (operation-specific):
 633          *   - ignoreMissingSource : The operation will simply succeed and do
 634          *                           nothing if the source file does not exist.
 635          *   - headers             : If supplied with a header name/value map, the backend will
 636          *                           reply with these headers when GETs/HEADs of the destination
 637          *                           file are made. Header values should be smaller than 256 bytes.
 638          *                           Content-Disposition headers can be longer, though the system
 639          *                           might ignore or truncate ones that are too long to store.
 640          *                           Existing headers will remain, but these will replace any
 641          *                           conflicting previous headers, and headers will be removed
 642          *                           if they are set to an empty string.
 643          *                           Backends that don't support metadata ignore this. (since 1.21)
 644          *
 645          * $opts is an associative of boolean flags, including:
 646          *   - bypassReadOnly      : Allow writes in read-only mode (since 1.20)
 647          *
 648          * @par Return value:
 649          * This returns a Status, which contains all warnings and fatals that occurred
 650          * during the operation. The 'failCount', 'successCount', and 'success' members
 651          * will reflect each operation attempted for the given files. The StatusValue will be
 652          * considered "OK" as long as no fatal errors occurred.
 653          *
 654          * @param array $ops Set of operations to execute
 655          * @param array $opts Batch operation options
 656          * @return StatusValue
 657          * @since 1.20
 658          */
 659         final public function doQuickOperations( array $ops, array $opts = [] ) {
 660                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 661                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 662                 }
 663                 if ( !count( $ops ) ) {
 664                         return $this->newStatus(); // nothing to do
 665                 }
 666
 667                 $ops = $this->resolveFSFileObjects( $ops );
 668                 foreach ( $ops as &$op ) {
 669                         $op['overwrite'] = true; // avoids RTTs in key/value stores
 670                 }
 671
 672                 /** @noinspection PhpUnusedLocalVariableInspection */
 673                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 674
 675                 return $this->doQuickOperationsInternal( $ops );
 676         }
 677
 678         /**
 679          * @see FileBackend::doQuickOperations()
 680          * @param array $ops
 681          * @since 1.20
 682          */
 683         abstract protected function doQuickOperationsInternal( array $ops );
 684
 685         /**
 686          * Same as doQuickOperations() except it takes a single operation.
 687          * If you are doing a batch of operations, then use that function instead.
 688          *
 689          * @see FileBackend::doQuickOperations()
 690          *
 691          * @param array $op Operation
 692          * @return StatusValue
 693          * @since 1.20
 694          */
 695         final public function doQuickOperation( array $op ) {
 696                 return $this->doQuickOperations( [ $op ] );
 697         }
 698
 699         /**
 700          * Performs a single quick create operation.
 701          * This sets $params['op'] to 'create' and passes it to doQuickOperation().
 702          *
 703          * @see FileBackend::doQuickOperation()
 704          *
 705          * @param array $params Operation parameters
 706          * @return StatusValue
 707          * @since 1.20
 708          */
 709         final public function quickCreate( array $params ) {
 710                 return $this->doQuickOperation( [ 'op' => 'create' ] + $params );
 711         }
 712
 713         /**
 714          * Performs a single quick store operation.
 715          * This sets $params['op'] to 'store' and passes it to doQuickOperation().
 716          *
 717          * @see FileBackend::doQuickOperation()
 718          *
 719          * @param array $params Operation parameters
 720          * @return StatusValue
 721          * @since 1.20
 722          */
 723         final public function quickStore( array $params ) {
 724                 return $this->doQuickOperation( [ 'op' => 'store' ] + $params );
 725         }
 726
 727         /**
 728          * Performs a single quick copy operation.
 729          * This sets $params['op'] to 'copy' and passes it to doQuickOperation().
 730          *
 731          * @see FileBackend::doQuickOperation()
 732          *
 733          * @param array $params Operation parameters
 734          * @return StatusValue
 735          * @since 1.20
 736          */
 737         final public function quickCopy( array $params ) {
 738                 return $this->doQuickOperation( [ 'op' => 'copy' ] + $params );
 739         }
 740
 741         /**
 742          * Performs a single quick move operation.
 743          * This sets $params['op'] to 'move' and passes it to doQuickOperation().
 744          *
 745          * @see FileBackend::doQuickOperation()
 746          *
 747          * @param array $params Operation parameters
 748          * @return StatusValue
 749          * @since 1.20
 750          */
 751         final public function quickMove( array $params ) {
 752                 return $this->doQuickOperation( [ 'op' => 'move' ] + $params );
 753         }
 754
 755         /**
 756          * Performs a single quick delete operation.
 757          * This sets $params['op'] to 'delete' and passes it to doQuickOperation().
 758          *
 759          * @see FileBackend::doQuickOperation()
 760          *
 761          * @param array $params Operation parameters
 762          * @return StatusValue
 763          * @since 1.20
 764          */
 765         final public function quickDelete( array $params ) {
 766                 return $this->doQuickOperation( [ 'op' => 'delete' ] + $params );
 767         }
 768
 769         /**
 770          * Performs a single quick describe operation.
 771          * This sets $params['op'] to 'describe' and passes it to doQuickOperation().
 772          *
 773          * @see FileBackend::doQuickOperation()
 774          *
 775          * @param array $params Operation parameters
 776          * @return StatusValue
 777          * @since 1.21
 778          */
 779         final public function quickDescribe( array $params ) {
 780                 return $this->doQuickOperation( [ 'op' => 'describe' ] + $params );
 781         }
 782
 783         /**
 784          * Concatenate a list of storage files into a single file system file.
 785          * The target path should refer to a file that is already locked or
 786          * otherwise safe from modification from other processes. Normally,
 787          * the file will be a new temp file, which should be adequate.
 788          *
 789          * @param array $params Operation parameters, include:
 790          *   - srcs        : ordered source storage paths (e.g. chunk1, chunk2, ...)
 791          *   - dst         : file system path to 0-byte temp file
 792          *   - parallelize : try to do operations in parallel when possible
 793          * @return StatusValue
 794          */
 795         abstract public function concatenate( array $params );
 796
 797         /**
 798          * Prepare a storage directory for usage.
 799          * This will create any required containers and parent directories.
 800          * Backends using key/value stores only need to create the container.
 801          *
 802          * The 'noAccess' and 'noListing' parameters works the same as in secure(),
 803          * except they are only applied *if* the directory/container had to be created.
 804          * These flags should always be set for directories that have private files.
 805          * However, setting them is not guaranteed to actually do anything.
 806          * Additional server configuration may be needed to achieve the desired effect.
 807          *
 808          * @param array $params Parameters include:
 809          *   - dir            : storage directory
 810          *   - noAccess       : try to deny file access (since 1.20)
 811          *   - noListing      : try to deny file listing (since 1.20)
 812          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 813          * @return StatusValue
 814          */
 815         final public function prepare( array $params ) {
 816                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 817                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 818                 }
 819                 /** @noinspection PhpUnusedLocalVariableInspection */
 820                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 821                 return $this->doPrepare( $params );
 822         }
 823
 824         /**
 825          * @see FileBackend::prepare()
 826          * @param array $params
 827          */
 828         abstract protected function doPrepare( array $params );
 829
 830         /**
 831          * Take measures to block web access to a storage directory and
 832          * the container it belongs to. FS backends might add .htaccess
 833          * files whereas key/value store backends might revoke container
 834          * access to the storage user representing end-users in web requests.
 835          *
 836          * This is not guaranteed to actually make files or listings publically hidden.
 837          * Additional server configuration may be needed to achieve the desired effect.
 838          *
 839          * @param array $params Parameters include:
 840          *   - dir            : storage directory
 841          *   - noAccess       : try to deny file access
 842          *   - noListing      : try to deny file listing
 843          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 844          * @return StatusValue
 845          */
 846         final public function secure( array $params ) {
 847                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 848                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 849                 }
 850                 /** @noinspection PhpUnusedLocalVariableInspection */
 851                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 852                 return $this->doSecure( $params );
 853         }
 854
 855         /**
 856          * @see FileBackend::secure()
 857          * @param array $params
 858          */
 859         abstract protected function doSecure( array $params );
 860
 861         /**
 862          * Remove measures to block web access to a storage directory and
 863          * the container it belongs to. FS backends might remove .htaccess
 864          * files whereas key/value store backends might grant container
 865          * access to the storage user representing end-users in web requests.
 866          * This essentially can undo the result of secure() calls.
 867          *
 868          * This is not guaranteed to actually make files or listings publically viewable.
 869          * Additional server configuration may be needed to achieve the desired effect.
 870          *
 871          * @param array $params Parameters include:
 872          *   - dir            : storage directory
 873          *   - access         : try to allow file access
 874          *   - listing        : try to allow file listing
 875          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 876          * @return StatusValue
 877          * @since 1.20
 878          */
 879         final public function publish( array $params ) {
 880                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 881                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 882                 }
 883                 /** @noinspection PhpUnusedLocalVariableInspection */
 884                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 885                 return $this->doPublish( $params );
 886         }
 887
 888         /**
 889          * @see FileBackend::publish()
 890          * @param array $params
 891          */
 892         abstract protected function doPublish( array $params );
 893
 894         /**
 895          * Delete a storage directory if it is empty.
 896          * Backends using key/value stores may do nothing unless the directory
 897          * is that of an empty container, in which case it will be deleted.
 898          *
 899          * @param array $params Parameters include:
 900          *   - dir            : storage directory
 901          *   - recursive      : recursively delete empty subdirectories first (since 1.20)
 902          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 903          * @return StatusValue
 904          */
 905         final public function clean( array $params ) {
 906                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 907                         return $this->newStatus( 'backend-fail-readonly', $this->name, $this->readOnly );
 908                 }
 909                 /** @noinspection PhpUnusedLocalVariableInspection */
 910                 $scope = $this->getScopedPHPBehaviorForOps(); // try to ignore client aborts
 911                 return $this->doClean( $params );
 912         }
 913
 914         /**
 915          * @see FileBackend::clean()
 916          * @param array $params
 917          */
 918         abstract protected function doClean( array $params );
 919
 920         /**
 921          * Enter file operation scope.
 922          * This just makes PHP ignore user aborts/disconnects until the return
 923          * value leaves scope. This returns null and does nothing in CLI mode.
 924          *
 925          * @return ScopedCallback|null
 926          */
 927         final protected function getScopedPHPBehaviorForOps() {
 928                 if ( PHP_SAPI != 'cli' ) { // http://bugs.php.net/bug.php?id=47540
 929                         $old = ignore_user_abort( true ); // avoid half-finished operations
 930                         return new ScopedCallback( function () use ( $old ) {
 931                                 ignore_user_abort( $old );
 932                         } );
 933                 }
 934
 935                 return null;
 936         }
 937
 938         /**
 939          * Check if a file exists at a storage path in the backend.
 940          * This returns false if only a directory exists at the path.
 941          *
 942          * @param array $params Parameters include:
 943          *   - src    : source storage path
 944          *   - latest : use the latest available data
 945          * @return bool|null Returns null on failure
 946          */
 947         abstract public function fileExists( array $params );
 948
 949         /**
 950          * Get the last-modified timestamp of the file at a storage path.
 951          *
 952          * @param array $params Parameters include:
 953          *   - src    : source storage path
 954          *   - latest : use the latest available data
 955          * @return string|bool TS_MW timestamp or false on failure
 956          */
 957         abstract public function getFileTimestamp( array $params );
 958
 959         /**
 960          * Get the contents of a file at a storage path in the backend.
 961          * This should be avoided for potentially large files.
 962          *
 963          * @param array $params Parameters include:
 964          *   - src    : source storage path
 965          *   - latest : use the latest available data
 966          * @return string|bool Returns false on failure
 967          */
 968         final public function getFileContents( array $params ) {
 969                 $contents = $this->getFileContentsMulti(
 970                         [ 'srcs' => [ $params['src'] ] ] + $params );
 971
 972                 return $contents[$params['src']];
 973         }
 974
 975         /**
 976          * Like getFileContents() except it takes an array of storage paths
 977          * and returns a map of storage paths to strings (or null on failure).
 978          * The map keys (paths) are in the same order as the provided list of paths.
 979          *
 980          * @see FileBackend::getFileContents()
 981          *
 982          * @param array $params Parameters include:
 983          *   - srcs        : list of source storage paths
 984          *   - latest      : use the latest available data
 985          *   - parallelize : try to do operations in parallel when possible
 986          * @return array Map of (path name => string or false on failure)
 987          * @since 1.20
 988          */
 989         abstract public function getFileContentsMulti( array $params );
 990
 991         /**
 992          * Get metadata about a file at a storage path in the backend.
 993          * If the file does not exist, then this returns false.
 994          * Otherwise, the result is an associative array that includes:
 995          *   - headers  : map of HTTP headers used for GET/HEAD requests (name => value)
 996          *   - metadata : map of file metadata (name => value)
 997          * Metadata keys and headers names will be returned in all lower-case.
 998          * Additional values may be included for internal use only.
 999          *
1000          * Use FileBackend::hasFeatures() to check how well this is supported.
1001          *
1002          * @param array $params
1003          * $params include:
1004          *   - src    : source storage path
1005          *   - latest : use the latest available data
1006          * @return array|bool Returns false on failure
1007          * @since 1.23
1008          */
1009         abstract public function getFileXAttributes( array $params );
1010
1011         /**
1012          * Get the size (bytes) of a file at a storage path in the backend.
1013          *
1014          * @param array $params Parameters include:
1015          *   - src    : source storage path
1016          *   - latest : use the latest available data
1017          * @return int|bool Returns false on failure
1018          */
1019         abstract public function getFileSize( array $params );
1020
1021         /**
1022          * Get quick information about a file at a storage path in the backend.
1023          * If the file does not exist, then this returns false.
1024          * Otherwise, the result is an associative array that includes:
1025          *   - mtime  : the last-modified timestamp (TS_MW)
1026          *   - size   : the file size (bytes)
1027          * Additional values may be included for internal use only.
1028          *
1029          * @param array $params Parameters include:
1030          *   - src    : source storage path
1031          *   - latest : use the latest available data
1032          * @return array|bool|null Returns null on failure
1033          */
1034         abstract public function getFileStat( array $params );
1035
1036         /**
1037          * Get a SHA-1 hash of the file at a storage path in the backend.
1038          *
1039          * @param array $params Parameters include:
1040          *   - src    : source storage path
1041          *   - latest : use the latest available data
1042          * @return string|bool Hash string or false on failure
1043          */
1044         abstract public function getFileSha1Base36( array $params );
1045
1046         /**
1047          * Get the properties of the file at a storage path in the backend.
1048          * This gives the result of FSFile::getProps() on a local copy of the file.
1049          *
1050          * @param array $params Parameters include:
1051          *   - src    : source storage path
1052          *   - latest : use the latest available data
1053          * @return array Returns FSFile::placeholderProps() on failure
1054          */
1055         abstract public function getFileProps( array $params );
1056
1057         /**
1058          * Stream the file at a storage path in the backend.
1059          *
1060          * If the file does not exists, an HTTP 404 error will be given.
1061          * Appropriate HTTP headers (Status, Content-Type, Content-Length)
1062          * will be sent if streaming began, while none will be sent otherwise.
1063          * Implementations should flush the output buffer before sending data.
1064          *
1065          * @param array $params Parameters include:
1066          *   - src      : source storage path
1067          *   - headers  : list of additional HTTP headers to send if the file exists
1068          *   - options  : HTTP request header map with lower case keys (since 1.28). Supports:
1069          *                range             : format is "bytes=(\d*-\d*)"
1070          *                if-modified-since : format is an HTTP date
1071          *   - headless : only include the body (and headers from "headers") (since 1.28)
1072          *   - latest   : use the latest available data
1073          *   - allowOB  : preserve any output buffers (since 1.28)
1074          * @return StatusValue
1075          */
1076         abstract public function streamFile( array $params );
1077
1078         /**
1079          * Returns a file system file, identical to the file at a storage path.
1080          * The file returned is either:
1081          *   - a) A local copy of the file at a storage path in the backend.
1082          *        The temporary copy will have the same extension as the source.
1083          *   - b) An original of the file at a storage path in the backend.
1084          * Temporary files may be purged when the file object falls out of scope.
1085          *
1086          * Write operations should *never* be done on this file as some backends
1087          * may do internal tracking or may be instances of FileBackendMultiWrite.
1088          * In that latter case, there are copies of the file that must stay in sync.
1089          * Additionally, further calls to this function may return the same file.
1090          *
1091          * @param array $params Parameters include:
1092          *   - src    : source storage path
1093          *   - latest : use the latest available data
1094          * @return FSFile|null Returns null on failure
1095          */
1096         final public function getLocalReference( array $params ) {
1097                 $fsFiles = $this->getLocalReferenceMulti(
1098                         [ 'srcs' => [ $params['src'] ] ] + $params );
1099
1100                 return $fsFiles[$params['src']];
1101         }
1102
1103         /**
1104          * Like getLocalReference() except it takes an array of storage paths
1105          * and returns a map of storage paths to FSFile objects (or null on failure).
1106          * The map keys (paths) are in the same order as the provided list of paths.
1107          *
1108          * @see FileBackend::getLocalReference()
1109          *
1110          * @param array $params Parameters include:
1111          *   - srcs        : list of source storage paths
1112          *   - latest      : use the latest available data
1113          *   - parallelize : try to do operations in parallel when possible
1114          * @return array Map of (path name => FSFile or null on failure)
1115          * @since 1.20
1116          */
1117         abstract public function getLocalReferenceMulti( array $params );
1118
1119         /**
1120          * Get a local copy on disk of the file at a storage path in the backend.
1121          * The temporary copy will have the same file extension as the source.
1122          * Temporary files may be purged when the file object falls out of scope.
1123          *
1124          * @param array $params Parameters include:
1125          *   - src    : source storage path
1126          *   - latest : use the latest available data
1127          * @return TempFSFile|null Returns null on failure
1128          */
1129         final public function getLocalCopy( array $params ) {
1130                 $tmpFiles = $this->getLocalCopyMulti(
1131                         [ 'srcs' => [ $params['src'] ] ] + $params );
1132
1133                 return $tmpFiles[$params['src']];
1134         }
1135
1136         /**
1137          * Like getLocalCopy() except it takes an array of storage paths and
1138          * returns a map of storage paths to TempFSFile objects (or null on failure).
1139          * The map keys (paths) are in the same order as the provided list of paths.
1140          *
1141          * @see FileBackend::getLocalCopy()
1142          *
1143          * @param array $params Parameters include:
1144          *   - srcs        : list of source storage paths
1145          *   - latest      : use the latest available data
1146          *   - parallelize : try to do operations in parallel when possible
1147          * @return array Map of (path name => TempFSFile or null on failure)
1148          * @since 1.20
1149          */
1150         abstract public function getLocalCopyMulti( array $params );
1151
1152         /**
1153          * Return an HTTP URL to a given file that requires no authentication to use.
1154          * The URL may be pre-authenticated (via some token in the URL) and temporary.
1155          * This will return null if the backend cannot make an HTTP URL for the file.
1156          *
1157          * This is useful for key/value stores when using scripts that seek around
1158          * large files and those scripts (and the backend) support HTTP Range headers.
1159          * Otherwise, one would need to use getLocalReference(), which involves loading
1160          * the entire file on to local disk.
1161          *
1162          * @param array $params Parameters include:
1163          *   - src : source storage path
1164          *   - ttl : lifetime (seconds) if pre-authenticated; default is 1 day
1165          * @return string|null
1166          * @since 1.21
1167          */
1168         abstract public function getFileHttpUrl( array $params );
1169
1170         /**
1171          * Check if a directory exists at a given storage path.
1172          * Backends using key/value stores will check if the path is a
1173          * virtual directory, meaning there are files under the given directory.
1174          *
1175          * Storage backends with eventual consistency might return stale data.
1176          *
1177          * @param array $params Parameters include:
1178          *   - dir : storage directory
1179          * @return bool|null Returns null on failure
1180          * @since 1.20
1181          */
1182         abstract public function directoryExists( array $params );
1183
1184         /**
1185          * Get an iterator to list *all* directories under a storage directory.
1186          * If the directory is of the form "mwstore://backend/container",
1187          * then all directories in the container will be listed.
1188          * If the directory is of form "mwstore://backend/container/dir",
1189          * then all directories directly under that directory will be listed.
1190          * Results will be storage directories relative to the given directory.
1191          *
1192          * Storage backends with eventual consistency might return stale data.
1193          *
1194          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1195          *
1196          * @param array $params Parameters include:
1197          *   - dir     : storage directory
1198          *   - topOnly : only return direct child dirs of the directory
1199          * @return Traversable|array|null Returns null on failure
1200          * @since 1.20
1201          */
1202         abstract public function getDirectoryList( array $params );
1203
1204         /**
1205          * Same as FileBackend::getDirectoryList() except only lists
1206          * directories that are immediately under the given directory.
1207          *
1208          * Storage backends with eventual consistency might return stale data.
1209          *
1210          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1211          *
1212          * @param array $params Parameters include:
1213          *   - dir : storage directory
1214          * @return Traversable|array|null Returns null on failure
1215          * @since 1.20
1216          */
1217         final public function getTopDirectoryList( array $params ) {
1218                 return $this->getDirectoryList( [ 'topOnly' => true ] + $params );
1219         }
1220
1221         /**
1222          * Get an iterator to list *all* stored files under a storage directory.
1223          * If the directory is of the form "mwstore://backend/container",
1224          * then all files in the container will be listed.
1225          * If the directory is of form "mwstore://backend/container/dir",
1226          * then all files under that directory will be listed.
1227          * Results will be storage paths relative to the given directory.
1228          *
1229          * Storage backends with eventual consistency might return stale data.
1230          *
1231          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1232          *
1233          * @param array $params Parameters include:
1234          *   - dir        : storage directory
1235          *   - topOnly    : only return direct child files of the directory (since 1.20)
1236          *   - adviseStat : set to true if stat requests will be made on the files (since 1.22)
1237          * @return Traversable|array|null Returns null on failure
1238          */
1239         abstract public function getFileList( array $params );
1240
1241         /**
1242          * Same as FileBackend::getFileList() except only lists
1243          * files that are immediately under the given directory.
1244          *
1245          * Storage backends with eventual consistency might return stale data.
1246          *
1247          * Failures during iteration can result in FileBackendError exceptions (since 1.22).
1248          *
1249          * @param array $params Parameters include:
1250          *   - dir        : storage directory
1251          *   - adviseStat : set to true if stat requests will be made on the files (since 1.22)
1252          * @return Traversable|array|null Returns null on failure
1253          * @since 1.20
1254          */
1255         final public function getTopFileList( array $params ) {
1256                 return $this->getFileList( [ 'topOnly' => true ] + $params );
1257         }
1258
1259         /**
1260          * Preload persistent file stat cache and property cache into in-process cache.
1261          * This should be used when stat calls will be made on a known list of a many files.
1262          *
1263          * @see FileBackend::getFileStat()
1264          *
1265          * @param array $paths Storage paths
1266          */
1267         abstract public function preloadCache( array $paths );
1268
1269         /**
1270          * Invalidate any in-process file stat and property cache.
1271          * If $paths is given, then only the cache for those files will be cleared.
1272          *
1273          * @see FileBackend::getFileStat()
1274          *
1275          * @param array $paths Storage paths (optional)
1276          */
1277         abstract public function clearCache( array $paths = null );
1278
1279         /**
1280          * Preload file stat information (concurrently if possible) into in-process cache.
1281          *
1282          * This should be used when stat calls will be made on a known list of a many files.
1283          * This does not make use of the persistent file stat cache.
1284          *
1285          * @see FileBackend::getFileStat()
1286          *
1287          * @param array $params Parameters include:
1288          *   - srcs        : list of source storage paths
1289          *   - latest      : use the latest available data
1290          * @return bool All requests proceeded without I/O errors (since 1.24)
1291          * @since 1.23
1292          */
1293         abstract public function preloadFileStat( array $params );
1294
1295         /**
1296          * Lock the files at the given storage paths in the backend.
1297          * This will either lock all the files or none (on failure).
1298          *
1299          * Callers should consider using getScopedFileLocks() instead.
1300          *
1301          * @param array $paths Storage paths
1302          * @param int $type LockManager::LOCK_* constant
1303          * @param int $timeout Timeout in seconds (0 means non-blocking) (since 1.24)
1304          * @return StatusValue
1305          */
1306         final public function lockFiles( array $paths, $type, $timeout = 0 ) {
1307                 $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1308
1309                 return $this->wrapStatus( $this->lockManager->lock( $paths, $type, $timeout ) );
1310         }
1311
1312         /**
1313          * Unlock the files at the given storage paths in the backend.
1314          *
1315          * @param array $paths Storage paths
1316          * @param int $type LockManager::LOCK_* constant
1317          * @return StatusValue
1318          */
1319         final public function unlockFiles( array $paths, $type ) {
1320                 $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1321
1322                 return $this->wrapStatus( $this->lockManager->unlock( $paths, $type ) );
1323         }
1324
1325         /**
1326          * Lock the files at the given storage paths in the backend.
1327          * This will either lock all the files or none (on failure).
1328          * On failure, the StatusValue object will be updated with errors.
1329          *
1330          * Once the return value goes out scope, the locks will be released and
1331          * the StatusValue updated. Unlock fatals will not change the StatusValue "OK" value.
1332          *
1333          * @see ScopedLock::factory()
1334          *
1335          * @param array $paths List of storage paths or map of lock types to path lists
1336          * @param int|string $type LockManager::LOCK_* constant or "mixed"
1337          * @param StatusValue $status StatusValue to update on lock/unlock
1338          * @param int $timeout Timeout in seconds (0 means non-blocking) (since 1.24)
1339          * @return ScopedLock|null Returns null on failure
1340          */
1341         final public function getScopedFileLocks(
1342                 array $paths, $type, StatusValue $status, $timeout = 0
1343         ) {
1344                 if ( $type === 'mixed' ) {
1345                         foreach ( $paths as &$typePaths ) {
1346                                 $typePaths = array_map( 'FileBackend::normalizeStoragePath', $typePaths );
1347                         }
1348                 } else {
1349                         $paths = array_map( 'FileBackend::normalizeStoragePath', $paths );
1350                 }
1351
1352                 return ScopedLock::factory( $this->lockManager, $paths, $type, $status, $timeout );
1353         }
1354
1355         /**
1356          * Get an array of scoped locks needed for a batch of file operations.
1357          *
1358          * Normally, FileBackend::doOperations() handles locking, unless
1359          * the 'nonLocking' param is passed in. This function is useful if you
1360          * want the files to be locked for a broader scope than just when the
1361          * files are changing. For example, if you need to update DB metadata,
1362          * you may want to keep the files locked until finished.
1363          *
1364          * @see FileBackend::doOperations()
1365          *
1366          * @param array $ops List of file operations to FileBackend::doOperations()
1367          * @param StatusValue $status StatusValue to update on lock/unlock
1368          * @return ScopedLock|null
1369          * @since 1.20
1370          */
1371         abstract public function getScopedLocksForOps( array $ops, StatusValue $status );
1372
1373         /**
1374          * Get the root storage path of this backend.
1375          * All container paths are "subdirectories" of this path.
1376          *
1377          * @return string Storage path
1378          * @since 1.20
1379          */
1380         final public function getRootStoragePath() {
1381                 return "mwstore://{$this->name}";
1382         }
1383
1384         /**
1385          * Get the storage path for the given container for this backend
1386          *
1387          * @param string $container Container name
1388          * @return string Storage path
1389          * @since 1.21
1390          */
1391         final public function getContainerStoragePath( $container ) {
1392                 return $this->getRootStoragePath() . "/{$container}";
1393         }
1394
1395         /**
1396          * Get the file journal object for this backend
1397          *
1398          * @return FileJournal
1399          */
1400         final public function getJournal() {
1401                 return $this->fileJournal;
1402         }
1403
1404         /**
1405          * Convert FSFile 'src' paths to string paths (with an 'srcRef' field set to the FSFile)
1406          *
1407          * The 'srcRef' field keeps any TempFSFile objects in scope for the backend to have it
1408          * around as long it needs (which may vary greatly depending on configuration)
1409          *
1410          * @param array $ops File operation batch for FileBaclend::doOperations()
1411          * @return array File operation batch
1412          */
1413         protected function resolveFSFileObjects( array $ops ) {
1414                 foreach ( $ops as &$op ) {
1415                         $src = isset( $op['src'] ) ? $op['src'] : null;
1416                         if ( $src instanceof FSFile ) {
1417                                 $op['srcRef'] = $src;
1418                                 $op['src'] = $src->getPath();
1419                         }
1420                 }
1421                 unset( $op );
1422
1423                 return $ops;
1424         }
1425
1426         /**
1427          * Check if a given path is a "mwstore://" path.
1428          * This does not do any further validation or any existence checks.
1429          *
1430          * @param string $path
1431          * @return bool
1432          */
1433         final public static function isStoragePath( $path ) {
1434                 return ( strpos( $path, 'mwstore://' ) === 0 );
1435         }
1436
1437         /**
1438          * Split a storage path into a backend name, a container name,
1439          * and a relative file path. The relative path may be the empty string.
1440          * This does not do any path normalization or traversal checks.
1441          *
1442          * @param string $storagePath
1443          * @return array (backend, container, rel object) or (null, null, null)
1444          */
1445         final public static function splitStoragePath( $storagePath ) {
1446                 if ( self::isStoragePath( $storagePath ) ) {
1447                         // Remove the "mwstore://" prefix and split the path
1448                         $parts = explode( '/', substr( $storagePath, 10 ), 3 );
1449                         if ( count( $parts ) >= 2 && $parts[0] != '' && $parts[1] != '' ) {
1450                                 if ( count( $parts ) == 3 ) {
1451                                         return $parts; // e.g. "backend/container/path"
1452                                 } else {
1453                                         return [ $parts[0], $parts[1], '' ]; // e.g. "backend/container"
1454                                 }
1455                         }
1456                 }
1457
1458                 return [ null, null, null ];
1459         }
1460
1461         /**
1462          * Normalize a storage path by cleaning up directory separators.
1463          * Returns null if the path is not of the format of a valid storage path.
1464          *
1465          * @param string $storagePath
1466          * @return string|null
1467          */
1468         final public static function normalizeStoragePath( $storagePath ) {
1469                 list( $backend, $container, $relPath ) = self::splitStoragePath( $storagePath );
1470                 if ( $relPath !== null ) { // must be for this backend
1471                         $relPath = self::normalizeContainerPath( $relPath );
1472                         if ( $relPath !== null ) {
1473                                 return ( $relPath != '' )
1474                                         ? "mwstore://{$backend}/{$container}/{$relPath}"
1475                                         : "mwstore://{$backend}/{$container}";
1476                         }
1477                 }
1478
1479                 return null;
1480         }
1481
1482         /**
1483          * Get the parent storage directory of a storage path.
1484          * This returns a path like "mwstore://backend/container",
1485          * "mwstore://backend/container/...", or null if there is no parent.
1486          *
1487          * @param string $storagePath
1488          * @return string|null
1489          */
1490         final public static function parentStoragePath( $storagePath ) {
1491                 $storagePath = dirname( $storagePath );
1492                 list( , , $rel ) = self::splitStoragePath( $storagePath );
1493
1494                 return ( $rel === null ) ? null : $storagePath;
1495         }
1496
1497         /**
1498          * Get the final extension from a storage or FS path
1499          *
1500          * @param string $path
1501          * @param string $case One of (rawcase, uppercase, lowercase) (since 1.24)
1502          * @return string
1503          */
1504         final public static function extensionFromPath( $path, $case = 'lowercase' ) {
1505                 $i = strrpos( $path, '.' );
1506                 $ext = $i ? substr( $path, $i + 1 ) : '';
1507
1508                 if ( $case === 'lowercase' ) {
1509                         $ext = strtolower( $ext );
1510                 } elseif ( $case === 'uppercase' ) {
1511                         $ext = strtoupper( $ext );
1512                 }
1513
1514                 return $ext;
1515         }
1516
1517         /**
1518          * Check if a relative path has no directory traversals
1519          *
1520          * @param string $path
1521          * @return bool
1522          * @since 1.20
1523          */
1524         final public static function isPathTraversalFree( $path ) {
1525                 return ( self::normalizeContainerPath( $path ) !== null );
1526         }
1527
1528         /**
1529          * Build a Content-Disposition header value per RFC 6266.
1530          *
1531          * @param string $type One of (attachment, inline)
1532          * @param string $filename Suggested file name (should not contain slashes)
1533          * @throws FileBackendError
1534          * @return string
1535          * @since 1.20
1536          */
1537         final public static function makeContentDisposition( $type, $filename = '' ) {
1538                 $parts = [];
1539
1540                 $type = strtolower( $type );
1541                 if ( !in_array( $type, [ 'inline', 'attachment' ] ) ) {
1542                         throw new InvalidArgumentException( "Invalid Content-Disposition type '$type'." );
1543                 }
1544                 $parts[] = $type;
1545
1546                 if ( strlen( $filename ) ) {
1547                         $parts[] = "filename*=UTF-8''" . rawurlencode( basename( $filename ) );
1548                 }
1549
1550                 return implode( ';', $parts );
1551         }
1552
1553         /**
1554          * Validate and normalize a relative storage path.
1555          * Null is returned if the path involves directory traversal.
1556          * Traversal is insecure for FS backends and broken for others.
1557          *
1558          * This uses the same traversal protection as Title::secureAndSplit().
1559          *
1560          * @param string $path Storage path relative to a container
1561          * @return string|null
1562          */
1563         final protected static function normalizeContainerPath( $path ) {
1564                 // Normalize directory separators
1565                 $path = strtr( $path, '\\', '/' );
1566                 // Collapse any consecutive directory separators
1567                 $path = preg_replace( '![/]{2,}!', '/', $path );
1568                 // Remove any leading directory separator
1569                 $path = ltrim( $path, '/' );
1570                 // Use the same traversal protection as Title::secureAndSplit()
1571                 if ( strpos( $path, '.' ) !== false ) {
1572                         if (
1573                                 $path === '.' ||
1574                                 $path === '..' ||
1575                                 strpos( $path, './' ) === 0 ||
1576                                 strpos( $path, '../' ) === 0 ||
1577                                 strpos( $path, '/./' ) !== false ||
1578                                 strpos( $path, '/../' ) !== false
1579                         ) {
1580                                 return null;
1581                         }
1582                 }
1583
1584                 return $path;
1585         }
1586
1587         /**
1588          * Yields the result of the status wrapper callback on either:
1589          *   - StatusValue::newGood() if this method is called without parameters
1590          *   - StatusValue::newFatal() with all parameters to this method if passed in
1591          *
1592          * @param ... string
1593          * @return StatusValue
1594          */
1595         final protected function newStatus() {
1596                 $args = func_get_args();
1597                 if ( count( $args ) ) {
1598                         $sv = call_user_func_array( [ 'StatusValue', 'newFatal' ], $args );
1599                 } else {
1600                         $sv = StatusValue::newGood();
1601                 }
1602
1603                 return $this->wrapStatus( $sv );
1604         }
1605
1606         /**
1607          * @param StatusValue $sv
1608          * @return StatusValue Modified status or StatusValue subclass
1609          */
1610         final protected function wrapStatus( StatusValue $sv ) {
1611                 return $this->statusWrapper ? call_user_func( $this->statusWrapper, $sv ) : $sv;
1612         }
1613
1614         /**
1615          * @param string $section
1616          * @return ScopedCallback|null
1617          */
1618         protected function scopedProfileSection( $section ) {
1619                 if ( $this->profiler ) {
1620                         call_user_func( [ $this->profiler, 'profileIn' ], $section );
1621                         return new ScopedCallback( [ $this->profiler, 'profileOut' ] );
1622                 }
1623
1624                 return null;
1625         }
1626 }